Materials desirably made fire resistant include polymeric materials, both natural and synthetic, woven and nonwoven fabrics, fibers, matting and batting. From a chemical structure perspective, low flammability can be achieved by introducing ring structures, and side groups which are not readily oxidized. For example, aromatic polyimides show excellent fire resistance, but are too costly for routine use.
A more common approach is to introduce one or more fire-retardant constituents to an inherently flammable material, such as in the case of a flammable polymer. The additive can be a fire-retardant monomer which is copolymerized to some degree with the inherently flammable monomer. Alternatively, the additive can be an unreactive material which is coated onto the material post-production, or molded or extruded with a polymeric material in a physical blend. The inherently flammable material could also be reactively treated with a fire-retardant additive after polymer production, as in the chlorination of polymers such as polyethylene.
Compounds which have found use as fire-retardants include inorganic compounds such as antimony compounds, including antimony trioxide, antimony pentoxide, and sodium antimonate. Boron compounds such as zinc borate, boric acid and sodium borate. Alumina trihydrate and molybdenum oxides are also useful inorganic compounds.
Halogenated compounds have also been used, including decabromodiphenyl oxide, chlorendic acid, tetrabromophthalic anhydride, and similarly halogenated compounds. These halogenated compounds, especially chlorinated compounds, are often combined with the above-mentioned inorganic compounds, especially antimony-, iron-, cobalt-, nickel-, molybdenum-, and other metal-containing compounds, to produce synergistic fire-retarding effects.